Blue horizontal line on the left side of the screen

Hi dear Apple Team,

Today while using my cellphone just normally like everyday, there appeared a blue horizontal line on the left side of the screen just from itself and I reset the phone 2-3 times in a row but the blue line does still appear on the screen. When I take a screenshot, it doesn’t appear on the screenshot but still is on my screen!

I would appreciate your help by giving me some steps to help to avoid this blue line or change of my phone into a new one.

Regards